How to create little flanges on the bottom of the bottle
You may do it fast using the inset tool.



Add a circle with 72 vertices- set it in a Tool Shelf (T).


Extrude it inwards (E) and add two edge loops (Ctrl+R). Select the whole face loop with Alt+RMB, then press I twice and set the inset's scale. Finally extrude the inseted faces upwards, add addictional loopcut in the middle and rotate it a bit (R).


Add a subsurf modifier (Ctrl+3 in Object Mode). Lower the middle loopcut a bit. Press Ctrl+Numpad+ to increase the selection area. Press Shift+E to crease it. Finally add a smooth shading and recalculate normals if needed (Ctrl+N).